The physical properties，micro-structure，mechanism of water and oil flow in porous media and nuclear magnetic resonance movable water saturation are systematically studied by means of constant-rate mercury injection technique，nuclear magnetic resonance，centrifugal experiment and waterflood experiment suitable for the poor quality of Jiangsu ultra-low-permeability oilfield.Meanwhile，the reservoir quality of different regions is also evaluated based on the five element classification method herein.The experimental results indicate that the physical property of Taizhou formation is better than that of Funing formation.The characteristic of porethroat distribution of different permeability is different.However，the pore distribution is less variable.The lower the reservoir permeability，the smaller porehroat.Between the main stream pore-throat and the reservoir permeability，there has a perfect relationship between the exponential function.The NMR experiment results demonstrate that the movable water saturation of Taizhou and Funing formation is 67.2%and 32.9%，respectively.During the waterflood process，the oil relative permeability drastically decreased as the increase of the water saturation but the water relative permeability increased slightly.The waterflood efficiency of the south-fault ultrapermeability was 54.1%on average.The multiphase flow experiment suggests that a certain amount of oil is still located in the large pores after the waterflood.The reservoir evaluation results using the five element classification method indicate that the physical quality of different oil regions ordered from good to bad is Taizhou formation，Chen2，Xuzhuang，Zhudun，Fangxiang and Xu31 Funing formation.